The invention relates to methods of and to apparatus for ascertaining the diameters of rod-shaped articles, particularly for ascertaining the diameters of filter rod sections, plain or filter cigarettes, cigars, cigarillos, cheroots and/or other rod-shaped articles of the tobacco processing industry.
The diameters of rod-shaped articles of the tobacco processing industry (hereinafter referred to as cigarettes with the understanding, however, that the procedure is or can be the same if the articles are cigars, cigarillos, cheroots or filter rod sections) are monitored for the purpose of segregating deformed cigarettes from satisfactory cigarettes. For example, greatly deformed cigarettes which have an oval or other non-circular cross-sectional outline should be segregated from satisfactory (round) cigarettes in order to avoid problems during gathering of cigarettes into arrays which are ready to be draped into blanks of paper, metallic foil and/or other wrapping material in a packing machine. Moreover, cigarettes which are not round will be turned out by a machine which is likely to require adjustment, i.e., detection of cigarettes which are not exactly round is tantamount to detection of a defect in the cigarette making or processing machine.
In accordance with a presently preferred technique, the diameters of cigarettes are monitored by photoelectronic means including a radiation source which is placed adjacent the path of transport of a series of cigarettes in a cigarette maker or in a cigarette processing machine, and a transducer which generates signals in response to impingement of radiation issuing from the source or in response to interruption of such impingement. The cigarettes to be tested normally advance at right angles to their respective axes, and each cigarette interrupts the beam of radiation issuing from the source for an interval of time which is indicative of the diameter of the respective cigarette. In other words, the length of intervals of interruption of impingement of the beam of radiation upon the transducer of the photoelectronic detector is indicative of the monitored diameter of the respective cigarette. Signals which are generated by the transducer are processed in a suitable evaluating circuit so that each processed signal denotes the diameter of the respective cigarette. A comparison of detected diameters with a desired value indicates whether or not the diameters of tested articles are satisfactory.
A single measurement, i.e., with a single photoelectronic detector, does not invariably ensure accurate determination of the shape of a rod-shaped article. For example, one side of a cigarette can be flattened while the remainder of the cigarette exhibits an acceptable circular shape. Therefore, many presently known apparatus which are used to ascertain the diameters of cigarettes employ a plurality of photoelectronic detectors with radiation sources distributed in such a way that the beams of radiation are inclined relative to each other. This renders it possible to ascertain several diameters and to generate signals which are thereupon compared with each other or with a signal denoting the desired diameter of a cigarette in order to obtain a more reliable indication concerning the actual cross-sectional outline of each of a series of successively tested cigarettes. Reference may be had, for example, to U.S. Pat. No. 4,011,950. A drawback of the patented apparatus is that it must rely on a plurality of detectors and that it must employ a rather complex circuitry which evaluates signals from the transducers of several discrete detectors. Moreover, the results of measurements are still unreliable.